Molten lava cakes with homemade whipped cream. I use an epicurious recipe without the sauce. They can be fully prepared and kept in the fridge (along with the whipped cream), ready to bake during dinner.... use a timer so they don't overcook if you're, um. distracted! Delicious, warm, sensual and amazingly simple.

Beranbaum's chocolate torte needs only three things: chocolate, butter and eggs. For the amount of effort, the result is surprisingly silky, decadent, luscious and chocolatey. Needless to say, use the best chocolate you can find:

all of the suggestions thus far are great. i'll just add that although i know you said you don't want to do something dipped in chocolate, i'm a big believer in interaction for situations like this. chocolate fondue with an assortment of items for dipping can make for a pretty sensual experience...you're dipping things, feeding them to each other, and attending to the errant drips & smears of chocolate that are bound to end up on your date's hands or the corners of their mouth...